The French reinforcements arrived Sunday from nearby Gabon, bringing the total French military force in the capital, Bangui, to nearly 600, Col. Thierry Burkhard told The Associated Press Sunday. The troops are to protect French residents in the capital, which many fear will be attacked by the rebels.

As fears mounted that the rebels would attack Bangui, a city of 600,000, President Francois Bozize imposed a curfew from 7 p.m. until 5 a.m.

Bozize earlier appealed to France for help against the rebels, but French President Francois Hollande's government said it would only protect French interests and would not prop up the Bangui government.

The African Union is attempting to set up negotiations in Gabon between the Bozize government and the rebels.

The rebel forces have seized at least 10 cities across the sparsely populated north of the country. Residents in the capital now fear the insurgents could attack at any time, despite assurances by rebel leaders that they are willing to engage in dialogue instead of attacking Bangui.

On Saturday the rebels seized the city of Sibut, 185 kilometers (114 miles) from Bangui.

Sibut, a key transportation hub, fell without a shot being fired because the Central African Republic army and forces from neighboring Chad had pulled back to Damara, 75 kilometers (46 miles) from Bangui on Friday, said Minister of Territorial Administration Josie Binoua.

Neighboring African countries have agreed to send more forces to support the Bozize government.

Representatives from the 10-nation Economic Community of Central African States, or ECCAS, agreed at a meeting in Gabon Friday to send forces to CAR, but did not did not specify how many troops would be sent or how quickly the military assistance would arrive.

The ECCAS states, with more than 500 soldiers via their regional peacekeeping force in Central Africa, over the weekend warned the rebels to halt their advances.

"ECCAS forces are on high alert, and the city of Damara is the limit not to cross," said Antonio Di Garcia, the ECCAS representative in Bangui. He urged the government forces and the rebels to hold to their current positions and to begin dialogue.

The ongoing instability prompted the United States to evacuate about 40 people, including the U.S. ambassador, from Bangui on an U.S. Air Force plane bound for Kenya, said U.S. officials who insisted on anonymity because they weren't authorized to discuss the operation.

The United States has special forces troops in the country who are assisting in the hunt for Joseph Kony, the fugitive rebel leader of another rebel group known as the Lord's Resistance Army. The U.S. special forces remain in the country, the U.S. military's Africa Command said from its headquarters in Stuttgart, Germany.

The evacuation of the U.S. diplomats came after criticism of how the U.S. handled diplomatic security before and during the attack on its consulate in Benghazi, Libya, on Sept. 11. The ambassador and three other Americans were killed in that attack.